Avalanche forecast

Northwest Coastal

Feb 1 – 2, 2015Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

As snow accumulates on Monday, the Avalanche Danger will rise. Expect reactive new storm slabs to form.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–5
    In the mid snowpack there are a few crusts which may be reactive with the potential for large avalanches. Although less likely to trigger, these persistent weak layers may "wake-up" in response to a large trigger such as a cornice fall.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Snowfall and wind on Sunday night and Monday will build new storms slabs. Watch for increased triggering in wind-exposed terrain.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Monday

Weather Forecast

Another pacific frontal system will bring snowfall to the coast on Monday. Lingering flurries are expected on Tuesday before a weak dry ridge of high pressure builds on Wednesday. Sunday night and Monday: Up to 20cm of snow / Strong southwest winds / Freezing level at valley bottom Tuesday: Very light snowfall and broken cloud / Moderate southwest winds / Freezing level at valley bottom Wednesday: Broken cloud / Moderate southwest winds / Freezing level at valley bottom

Avalanche Summary

Several storm slabs to size 2.5 were reported in the wake of Thursday night's storm. With more snow and wind on the way on Sunday, I'd expect continued storm slab activity. It's important to keep in mind, a surface avalanche in motion may be what it takes to trigger deeper, more destructive persistent slab avalanches.

Snowpack Summary

Prior to the weekend, moderate to heavy snowfall and strong southwest winds built deep storm slabs which are expected to be most reactive in wind-exposed terrain. More snow and wind forecast for Sunday night and Monday will add to this ongoing storm slab problem.About 100cm below the surface, you'll likely find a rain crust which was buried on January 26. Limited observations suggest the overlying slab may have a reasonable bond at this interface.A rain crust and/or surface hoar layer buried mid-January may be found at variable depths (in some areas up to 150cm below the surface). This layer is likely gaining strength, although I would keep it on my radar especially at higher elevations as it was the culprit in much of the recent destructive avalanche activity.The November crust/ facet combo near the bottom of the snowpack is thought to be generally well bonded. However, this deep and destructive layer is still reported to be reactive in the far north of the region.

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